3.2.1 Outline the structure of the central processing unit (CPU) including the functions of the control unit (CU), the arithmetic and logic unit (ALU), primary memory and address buses.
The central processing unit (CPU) is the primary element of a computer system that carries out the instructions of a computer program. The central processing unit carries out each instruction of the program in sequence, to perform the basic arithmetical, logical, and input/output operations of the system.
3.2.2 Outline the meaning of the terms bit (b) and byte (B) and their derivatives.
A bit (Binary digIT) can be defined as a variable or computed quantity that can have only two possible values. These two values are often interpreted as binary digits and are usually denoted by the numerical digits 0 and 1. A byte is 8 bits. Kilobyte is 1024^1 (2^10)
bytes, a Megabyte is 1024^2 (2^20) bytes, a Gigabyte is 1024^3 (2^30) bytes and a Terabyte is 1024^4 (2^40) bytes.
3.2.3 Outline the meaning of the terms word, register and address and their use in the storage of data and instructions.
- Word, or “word size”, is a fixed group of bits that are handled together by the machine. It can vary from machine to machine but in general the sizes of buses and registers are multiples of the word size. So if the word size is 10 then the busses might be able to care 30 at a time.
- Registers are non-volatile memory locations that store "must happen" instructions of data. They can also be accessed quickly.
- Address-where something is at in memory or its index. Addresses are used so that items in memory can be found more quickly because they have an index.
3.2.4 Outline the steps in the machine instruction cycle: fetch, decode, execute and store.
Fetch is where the computer gets instructions from the program and gives them to the decoder. This is a "one at a time" process. Decode is where the computer converts the instructions into machine language(1’s and 0’s remember) and identifies the processes that need to take place to handle those instructions. Execute does what it says. It executes or does the processes that need to be done for the instructions objectives to be completed.
Once each step has done it’s job the instructions are threaded back up to the fetch (Stored) where it will say “okay, I’m done.” to the program.
3.2.5 Outline the characteristics of primary memory and the difference between volatile and non-volatile memory.
Primary memories are types of memory such as RAM, ROM, cache, etc… Primary Memory differs from Secondary Memory in that it is directly accessible by the CPU. Volatile memory is memory that will be lost if the computer is turned off (RAM). Non-volatile memory is memory that will not be lost if the computer is turned off (ROM). Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed.
Type of Storage
Typical memory sizes.
Random Access Memory ( RAM )
2-4 GB
Read Only Memory ( ROM )
4MB
Cache
up to 16MB cache
3.2.6 Outline the characteristics of secondary memory and define sequential and direct access.
Secondary Memory:
Secondary memory is where most of the information that is not needed to be stored in primary memory or is too large to store in a computer's hard drive. This type of memory is usually used as a form of backup. Both data and programs can be stored in these types of mediums. There are two main types of data storage for secondary memory, these being sequential access and direct access.
Sequential Access:
This type of access is usually used for reading or writing data records in
sequential order, that is, one record after the other. To read record 10, for example, you would first need to read records 1 through 9. In general, payroll programs have to access data files containing all the data on all of a company's employees, and they accesses this data one record at a time, one after the other.
Examples of sequential access include magnetic tape.
Direct Access:
Direct access allows the system to read and write records in any order. This type of access would be used, for example, in a supermarket where details of all of the items for sale are held in a file, the computer needs to locate an item quickly by moving directly to its record. Direct access requires some kind of index to be held on the medium storing the data.
The most common examples of a secondary memory direct access medium is Flash Memory.
CD's, DVD's and hard disks are both direct and sequential access, as they first access directly to the beginning of the stored data, but act sequentially once they start reading the data.
3.2.7 Outline the function of a microprocessor designed to perform one or a limited number of functions (within a car, washing machine and so on).
Microprocessor have two main memory types; RAM and ROM. RAM contains bytes of information, and the microprocessor can read or write to those bytes. The problem with RAM chips is that they forget everything once the power goes off, so a ROM chip is needed. A ROM chip is programmed with a permanent collection of instructions. For example, in a washing machine, a microprocessor will take the program choice set by the user and will then control the washing machine actuators and run the selected program as selected by the user.
3.2.8 Discuss the features, advantages, disadvantages and applications of specific input and output devices and the media used by each.
All the useful information on this topic can be found in the following website: http://www.igcseict.info/
3.2.9 Outline recent developments in computer system architecture including processor architecture, primary memory technologies and secondary memory devices.
3.2.1 Outline the structure of the central processing unit (CPU) including the functions of the control unit (CU), the arithmetic and logic unit (ALU), primary memory and address buses.
The central processing unit (CPU) is the primary element of a computer system that carries out the instructions of a computer program. The central processing unit carries out each instruction of the program in sequence, to perform the basic arithmetical, logical, and input/output operations of the system.
3.2.2 Outline the meaning of the terms bit (b) and byte (B) and their derivatives.
A bit (Binary digIT) can be defined as a variable or computed quantity that can have only two possible values. These two values are often interpreted as binary digits and are usually denoted by the numerical digits 0 and 1. A byte is 8 bits. Kilobyte is 1024^1 (2^10)
bytes, a Megabyte is 1024^2 (2^20) bytes, a Gigabyte is 1024^3 (2^30) bytes and a Terabyte is 1024^4 (2^40) bytes.
3.2.3 Outline the meaning of the terms word, register and address and their use in the storage of data and instructions.
- Word, or “word size”, is a fixed group of bits that are handled together by the machine. It can vary from machine to machine but in general the sizes of buses and registers are multiples of the word size. So if the word size is 10 then the busses might be able to care 30 at a time.
- Registers are non-volatile memory locations that store "must happen" instructions of data. They can also be accessed quickly.
- Address-where something is at in memory or its index. Addresses are used so that items in memory can be found more quickly because they have an index.
3.2.4 Outline the steps in the machine instruction cycle: fetch, decode, execute and store.
Fetch is where the computer gets instructions from the program and gives them to the decoder. This is a "one at a time" process.
Decode is where the computer converts the instructions into machine language(1’s and 0’s remember) and identifies the processes that need to take place to handle those instructions.
Execute does what it says. It executes or does the processes that need to be done for the instructions objectives to be completed.
Once each step has done it’s job the instructions are threaded back up to the fetch (Stored) where it will say “okay, I’m done.” to the program.
3.2.5 Outline the characteristics of primary memory and the difference between volatile and non-volatile memory.
Primary memories are types of memory such as RAM, ROM, cache, etc… Primary Memory differs from Secondary Memory in that it is directly accessible by the CPU. Volatile memory is memory that will be lost if the computer is turned off (RAM). Non-volatile memory is memory that will not be lost if the computer is turned off (ROM). Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed.
3.2.6 Outline the characteristics of secondary memory and define sequential and direct access.
Secondary Memory:
Secondary memory is where most of the information that is not needed to be stored in primary memory or is too large to store in a computer's hard drive. This type of memory is usually used as a form of backup. Both data and programs can be stored in these types of mediums. There are two main types of data storage for secondary memory, these being sequential access and direct access.
Sequential Access:
This type of access is usually used for reading or writing data records in
sequential order, that is, one record after the other. To read record 10, for example, you would first need to read records 1 through 9. In general, payroll programs have to access data files containing all the data on all of a company's employees, and they accesses this data one record at a time, one after the other.
Examples of sequential access include magnetic tape.
Direct Access:
Direct access allows the system to read and write records in any order. This type of access would be used, for example, in a supermarket where details of all of the items for sale are held in a file, the computer needs to locate an item quickly by moving directly to its record. Direct access requires some kind of index to be held on the medium storing the data.
The most common examples of a secondary memory direct access medium is Flash Memory.
CD's, DVD's and hard disks are both direct and sequential access, as they first access directly to the beginning of the stored data, but act sequentially once they start reading the data.
3.2.7 Outline the function of a microprocessor designed to perform one or a limited number of functions (within a car, washing machine and so on).
Microprocessor have two main memory types; RAM and ROM. RAM contains bytes of information, and the microprocessor can read or write to those bytes. The problem with RAM chips is that they forget everything once the power goes off, so a ROM chip is needed. A ROM chip is programmed with a permanent collection of instructions. For example, in a washing machine, a microprocessor will take the program choice set by the user and will then control the washing machine actuators and run the selected program as selected by the user.
3.2.8 Discuss the features, advantages, disadvantages and applications of specific input and output devices and the media used by each.
All the useful information on this topic can be found in the following website:
http://www.igcseict.info/
3.2.9 Outline recent developments in computer system architecture including processor architecture, primary memory technologies and secondary memory devices.
http://dis-dpcs.wikispaces.com/3.2.9+Recent+Tech+Developments
Technical details are not required unless introduced in the case study.
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